复合载荷下脆性材料紧凑拉伸试件疲劳裂纹的预制

本文针对脆性材料的紧凑拉伸（CT）试件，提出了在复合疲劳载荷作用下预制疲劳裂纹的新方法，用此方法预制出7060-T6铝合金的CT试件疲劳裂纹并测试其断裂韧性。由于采用了框架结构和螺旋结构在CT试件的两侧面施加压缩载荷，在拉伸疲劳载荷作用下产生与之方向相反的压缩疲劳载荷，形成复合疲劳载荷，引起应力强度因子范围ΔK的下降，导致裂纹扩展速率的降低，从而控制了疲劳预制裂纹长度。此压缩疲劳载荷值用贴电阻片方法和组成全桥原理测定出。在一定拉伸疲劳载荷和压缩载荷下，可成功地预制出所需的疲劳裂纹长度。

Fatigue Precracking for Brittle Materials in Compact Tension Specimen by Combined Loading

A new fatigue precracking method for brittle materials was proposed, and it was based on compact tension specimens with combined loading treatment. The method was applied to 7060 T6 aluninum alloy specimens for measuring its fracture toughness. In the method, a frame structure with screw device was employed to impose a compressive load on the two flanks of specimen,and this resulted in the reduction of crack propagation rate in tension fatigue, and therefore controlled the length of fatigue precracking. The experiment showed that with a giving load of tension fatigue and a proper side compression, a demanded crack length can be prefabricated successfully.